Thermal protection: Non-homogeneous heat transfer through an axial fan

Transcription

1 Thermal protection: Non-homogeneous heat transfer through an axial fan Dipl.-Ing Markus Riesterer, Prof. Dr.-Ing Bettina Frohnapfel, Institut of Fluid Mechanics Dr.-Ing. Heinrich Reister, Dr.-Ing. Thomas Binner, Daimler AG KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 Contents Objective target Overview: Modelling of fans Isothermal test rig Experimental Analysis Numerical Analysis Thermal test rig Experimental Analysis Numerical Analysis Summary & outlook Markus Riesterer

3 Objective target: Model of the heat flux in an axial fan State of the art: Task: Calculation of the temperature and velocity field High quality Multiple Reference Frame (MRF) Volume-Force-Model Temperature field inaccurate Experimental data required Low numerical effort Markus Riesterer

4 Objective target: Model of the heat flux in an axial fan Task: Calculation of the temperature and velocity field High quality Low numerical effort State of the art: Multiple Reference Frame (MRF) Volume-Force-Model Temperature field inaccurate Experimental data required Experiment: Velocity field (FSM) Temperature field Markus Riesterer

5 Objective target: Model of the heat flux in an axial fan Task: Calculation of the temperature and velocity field High quality Low numerical effort State of the art: Multiple Reference Frame (MRF) Volume-Force-Model Temperature field inaccurate Experimental data required Experiment: Velocity field (FSM) Temperature field Simulation unst. RANS: Velocity field Temperature field Markus Riesterer

6 Objective target: Model of the heat flux in an axial fan Task: Calculation of the temperature and velocity field High quality Low numerical effort State of the art: Multiple Reference Frame (MRF) Volume-Force-Model Temperature field inaccurate Experimental data required Data basis for further models Experiment: Velocity field (FSM) Temperature field Validation Quality Optimisation of the MRF - model Simulation unst. RANS: Velocity field Temperature field Harmonic Balance Approach (HB) Markus Riesterer

7 Overview: Modelling of fans Body Force Model (BFM) or Volume Force Model: (steady) Pressure jump and swirl applied on a disk or fan surface depending on flow rate (often only pressure jump included) Data out of experimental fan blade curves Correction for each case needed Markus Riesterer

8 Overview: Modelling of fans Body Force Model (BFM) or Volume Force Modell (steady) Pressure jump and swirl applied on a disk or fan surface depending on flow rate (often only pressure jump included) Data out of experimental fan blade curves Correction for each case needed Multiple Reference Frame Model (MRF): (steady) Fan region is modelled in a rotating frame of reference (Centripetal and Coriolis force) Other regions are modelled stationary Markus Riesterer

9 Overview: Modelling of fans Body Force Model (BFM) or Volume Force Model: (steady) Pressure jump and swirl applied on a disk or fan surface depending on flow rate (often only pressure jump included) Data out of experimental fan blade curves Correction for each case needed Multiple Reference Frame Model (MRF): (steady) Fan region is modelled in a rotating frame of reference (Centripetal and Coriolis force) Other regions are modelled stationary Mixing Plane Model (MPM): (steady) Circumferential average of the MRF solution at interfaces Convergence problems with large backflow Markus Riesterer

10 Overview: Modelling of fans Body Force Model (BFM) or Volume Force Model: (steady) Pressure jump and swirl applied on a disk or fan surface depending on flow rate (often only pressure jump included) Data out of experimental fan blade curves Correction for each case needed Multiple Reference Frame Model (MRF): (steady) Fan region is modelled in a rotating frame of reference (Centripetal and Coriolis force) Other regions are modelled stationary Mixing Plane Model (MPM): (steady) Circumferential average of the MRF solution at interfaces Convergence problems with large backflow Sliding Mesh Method: (unsteady) Rotation modelled by a sliding mesh High computational effort Markus Riesterer

11 Experimental research KIT: Analysis of flow field: constant temperature Measurement: Particle Image Velocimetry (PIV) Markus Riesterer

12 Experimental research KIT: Analysis of flow field: constant temperature Measurement: Particle Image Velocimetry (PIV) Daimler Cooler test rig FNT: Heat transfer: air temperature direct behind fan Different operating points: Homogeneous / non-homogeneous flow field (velocity)(obstruction, charge-air cooler) Homogeneous / non-homogeneous heat sources (charge-air cooler, water cooler, coolant mass flow, heat quantity) Rotational speed (rpm) Markus Riesterer

13 Isothermal test rig PIV: Tangential velocity (without plate) Experimental research: upper side lower side Markus Riesterer

14 Isothermal test rig URANS: Tangential velocity (without plate) Experiment: URANS Markus Riesterer

15 Isothermal test rig MRF: Tangential velocity (with plate) URANS Multiple Reference Frame (MRF) Markus Riesterer

16 Isothermal test rig MRF: Tangential velocity (with plate) URANS Multiple Reference Frame (MRF) Rotor 30 rotated Markus Riesterer

17 Isothermal test rig MRF 3: Axial velocity (with plate) URANS Mean Multiple Reference Frame (MRF) (3 Positions, rotated by 30 ) Markus Riesterer

18 Isothermal test rig Experiment: CFD: PIV: measurement of the velocity components (direct behind the fan) Pressure sensors: pressure gradient over the fan URANS MRF Mean of MRF simulation with different blade positions Main results: Good agreement of the pressure gradient Outflow of the fan too centric (URANS and MRF) MRF solution depends on the blade position (static) Mean of several MRF simulations leads approximately to URANS result Markus Riesterer

19 Thermal test rig Charge-air cooler Radiator Water cooler Fan Measuring plane Plate Inlet Outlet Markus Riesterer

20 Thermal test rig Experiment: Modul A VIIb (inhom. T, hom. v) Modul Plate Rotational speed [rpm] Water cooler (Q) [kw] Air cooler (Q) [kw] A yes ,0 7,5 25,8 25,8 23,1 23,4 NaN NaN 26,9 26,7 27,8 26,9 24,8 23,1 21,8 20,1 NaN NaN 23,3 26,1 26,8 26,5 24,3 22,2 19,6 19,9 NaN NaN 19,6 19,6 26,2 25,7 24,0 19,7 19,9 20,1 NaN NaN 20,1 19,5 21,8 27,8 19,5 24,7 19,9 20,5 20,5 20,8 21,1 22,2 20,4 19,6 26,7 33,9 26,7 Installation: - Air cooler - Radiator - Water Cooler - Plate 41,1 20,6 20,5 20,4 21,1 21,6 22,1 21,9 20,4 19,7 31,1 48,3 20,3 20,1 20,5 21,5 22,3 22,9 24,2 21,7 25,4 32,5 22,6 27,4 21,7 20,7 21,1 21,3 22,0 37,4 38,1 37,1 25,8 31,9 48,3 29,1 21,8 21,2 29,2 43,9 45,8 40,9 26,5 32,6 40,3 44,5 30,2 25,2 29,7 40,9 42,8 38, Markus Riesterer

21 Thermal test rig URANS: Modul A VIIb (inhom. T, hom. v) Distance plate measuring plane: 55mm Experiment: Simulation: URANS 25,8 25,8 23,1 23,4 NaN NaN 26,9 26,7 27,8 26,9 24,8 23,1 21,8 20,1 NaN NaN 23,3 26,1 26,8 26,5 24,3 22,2 19,6 19,9 NaN NaN 19,6 19,6 26,2 25,7 24,0 19,7 19,9 20,1 NaN NaN 20,1 19,5 21,8 27,8 19,5 26,7 24,7 19,9 20,5 20,5 20,8 21,1 22,2 20,4 19,6 26,7 33,9 41,1 20,6 20,5 20,4 21,1 21,6 22,1 21,9 20,4 19,7 31,1 48,3 20,3 20,1 20,5 21,5 22,3 22,9 24,2 21,7 25,4 32,5 22,6 27,4 21,7 20,7 21,1 21,3 22,0 37,4 38,1 37,1 25,8 31,9 48,3 29,1 21,8 21,2 29,2 43,9 45,8 40,9 26,5 32,6 40,3 44,5 30,2 25,2 29,7 40,9 42,8 38, Markus Riesterer

22 Thermal test rig MRF: Modul A VIIb (inhom. T, hom. v) Distance plate measuring plane: 55mm Experiment: Simulation: MRF 25,8 25,8 23,1 23,4 NaN NaN 26,9 26,7 27,8 26,9 24,8 23,1 21,8 20,1 NaN NaN 23,3 26,1 26,8 26,5 24,3 22,2 19,6 19,9 NaN NaN 19,6 19,6 26,2 25,7 24,0 19,7 19,9 20,1 NaN NaN 20,1 19,5 21,8 27,8 19,5 26,7 24,7 19,9 20,5 20,5 20,8 21,1 22,2 20,4 19,6 26,7 33,9 41,1 20,6 20,5 20,4 21,1 21,6 22,1 21,9 20,4 19,7 31,1 48,3 20,3 20,1 20,5 21,5 22,3 22,9 24,2 21,7 25,4 32,5 22,6 27,4 21,7 20,7 21,1 21,3 22,0 37,4 38,1 37,1 25,8 31,9 48,3 29,1 21,8 21,2 29,2 43,9 45,8 40,9 26,5 32,6 40,3 44,5 30,2 25,2 29,7 40,9 42,8 38, Markus Riesterer

23 Modelling ModMRF Correction of the temperature Basis: MRF-simulation & operation point Mean abode time of the fluid on the fan Rotation of the flow field based by the rotational speed Rotation of the temperature field: Markus Riesterer

24 Thermal test rig ModMRF Inlet Outlet Heat transfer from to Basis: No essential mixing of the temperature in the fan Task: Rotation and translation of the temperature caused by the fan Distance between inlet and outlet of the fan: measured Average velocity in each direction out of MRF simulation Rotation of the temp. field Translation in radial direction Markus Riesterer

25 Thermal test rig ModMRF: first approach MRF => Mean velocity field (with known inadequacy) => Temperature field at Objective: temperature field at Area : I) Average rotation of the temperature field from in the whole area with: Ib)Additional Average radial sweep for the whole fan Markus Riesterer

26 Thermal test rig ModMRF Ib: Modul A VIIb (inhom. T, hom. v) Distance plate measuring plane: 55mm Experiment: 25,8 25,8 23,1 23,4 NaN NaN 26,9 26,7 27,8 26,9 Simulation: ModMRF Ib) Tangential + radial sweep 24,8 23,1 21,8 20,1 NaN NaN 23,3 26,1 26,8 26,5 24,3 22,2 19,6 19,9 NaN NaN 19,6 19,6 26,2 25,7 24,0 19,7 19,9 20,1 NaN NaN 20,1 19,5 21,8 27,8 19,5 26,7 24,7 19,9 20,5 20,5 20,8 21,1 22,2 20,4 19,6 26,7 33,9 41,1 20,6 20,5 20,4 21,1 21,6 22,1 21,9 20,4 19,7 31,1 48,3 20,3 20,1 20,5 21,5 22,3 22,9 24,2 21,7 25,4 32,5 22,6 27,4 21,7 20,7 21,1 21,3 22,0 37,4 38,1 37,1 25,8 31,9 48,3 29,1 21,8 21,2 29,2 43,9 45,8 40,9 26,5 32,6 40,3 44,5 30,2 25,2 29,7 40,9 42,8 38, Markus Riesterer

27 Summary Analysis of the velocity field PIV, MRF, Averaged MRF (blade positions) and URANS Good Agreement of the pressure gradient Average of several MRF leads to mean of URANS Underestimation of the downstream flow angle (especial radial) Flow is too centric Analysis of the thermal behaviour (Non-homogeneous temperature field) Experiment, MRF, ModMRF I + Ib and URANS Good agreement of the pressure gradient Temperature field too centric (as predicted) ModMRF models heat transfer like URANS Markus Riesterer

28 Outlook Isothermal test rig Averaged of MRF with more blade positions Question: Optimal value of blade positions Analysis of other turbulence model Thermal test rig ModMRF II Two Region method (cooperation with CD-adapco) Industrial test case (implementation in a car) Combination of several blade positions with ModMRF Markus Riesterer

29 Many thanks for your attention! Markus Riesterer